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| | Abstract | | Hybrid surface wave surveys were successfully applied along operational highways which had traffic flows of 300 to 1,500 vehicles per hour. The hybrid surface wave survey consists of an active multichannel surface wave survey and a 2-D linear array microtremor survey. A 10-kg wooden hammer was used to generate surface waves in active surveys. In contrast, vibration noises from traffic vehicles were recorded in passive surveys. The hybrid surface wave survey is characterized by using the same geophone array set along a roadside and by continuous data acquisition of active and passive surveys. Two dispersion curves, one is for a higher frequency part calculated from active data and the other is for a lower frequency part from passive data, are combined to form a single dispersion curve for a specific CMP in a survey line. Consequently, we could obtain clean dispersion curves not only from the active but also from the passive survey data, and successfully reconstruct 2-D S-wave velocity profiles along lines from shallow layers to substrata up to 50 m. The field tests demonstrated the hybrid surface wave method was quite capable for the delineation of diverse structure in embankments of highways even under heavy traffic condition. |
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